Idea Details

Agree, much needed.

please release these kind of experience for happy customize.
 

one of the must-haves

It would be more useful to have a granual override configration defined against profiles and record type. Do upvote the below idea if the idea sounds great.
https://trailblazer.salesforce.com/ideaView?id=0874V0000015IryQAE

Much needed Idea. 

agree.  should behave the same as the native actions.

@Sergio - Thanks for joining a screenshare with me and Eric Shih (also a PM).

Update: This is a bug (which is independent of this Idea). I'm not aware of a Known Issue for this so here's the problem scenario:
1. Open a standard navigation app where there's (for example) a New action override for Contact.
2. On the Case tab, click "New Case". New case form appears in a modal.
3. Click in the "Contact" field. See option "New Contact".
4. Select "New Contact" from the lookup.

Expected(?): The custom "Contact" form appears in a new modal which is displayed on top of the existing modal (or at least some scenario that is not like actual - see below for how we're going to address this).
Actual: The modal is dismissed (and any text entered there is gone) and the custom "Contact" form appears in the "Contacts" tab.

This was a regression introduced in Winter '20. In Summer '19 and earlier the 'New Contact' option simply didn't appear in the lookup because it's a custom action.

#safeharbor  The team has fixed the code to make it work like Summer '19 again. They are deploying that to Spring '20 in a patch ASAP. No plans to backport it to Winter '20 since users will be on Spring '20 very shortly.

@Tyson - We give more scrutiny to unanticipated data loss, loosely interpreted. I'm setting up a screenshare with Sergio and also talking with other PMs to get a crisper point of view on this. Stay tuned.

@Xander - you lose entered data in many cases...for example...creating a new Opportunity and need to add a related contact. When clicking "New Contact", the screen state changes and anything entered for the Opportunity is gone! This is a big deal in our org...in fact, one of our biggest complaints. Please work to find a solution ASAP if you can.  

@Amir - That's what I was thinking. It just sounded like maybe there was a more complex workflow that might change our approach.

@Xander,

As @Sergio suggested, why not just create a new interface i.e. modalActionOverride and apply the new UX process to that, this way you create an opt in for existing customers, whilst supporting the old functionality.

@Sergio - I don't totally follow your click path. Would you mind emailing me (xmitman@salesforce.com) so we can set up time for me to see a demo? The part about losing entered data is concerning and I'm not aware of that situation.

Well put Sergio...my thoughts exactly! 

@Xander, if you don't want to modify the current behaviour and implementation of the actionOverride, I'd suggest to keep all these thoughts for the LWC ones, to not make the same mistakes again.
If by any chance you want to push to get it fixed for the regular lightning components, you could create an "advancedActionOverride" or  "actionOverride2" (just kidding)

You need to understand that if the behaviour remains unchanged, it is quite frustrating for the platform users. In their eyes, it is just a relationship, and it is hard to explain why they can create records on the fly and keep working for some of them, and for the ones that has an override they have to start over with the previous record creation / modification.

In our case, the big bummer is not the fact that it looks different, but the fact that when using the "+ New XXX" that is using the standard, the user is allowed to create a record, and after saving, the user can continue with the previous request. If the object that is the target of the lookup has an action override all the information that the user has input so far will be lost !!

For example, when a user is creating a new Opportunity, the user can start filling some information related to the opportunty, and when he arrives to the lookup, if he is not able to find the account he wants, he will click on "+ New Account" to create a new one.

• If no "new" action overrides has been created, the "New Account" modal will appear, allowing the user to create the record and after saving, continue with the Opportunity where it was left off.
• If a "new" action override has been set-up, the "New Account" component will appear, but it will get rid of all the information that has been filled so far in the Opportunity", which is quite frustrating.

I'd say that not only what this idea is suggestng needs to be implemented, but also some event should be created so that the lightning component that has the override can "report back" the Id and the Name of the newly created record, so that the component that invoked it can fill the proper lookup with that information.

And since I'm here, I'll take the chance to suggest to allow the component that contains the override to "forward" the action to the standard, without having to do the redirect to the "?nooverride=1", which is a bit ugly :D

Kind Regards