I definitely see the use case, especially with the multi-day event you mentioned. Sadly it’s not possible to solve this problem future-proof.
Maybe the “required” functionality in general should be extendable by custom fields/plugins without overwriting each core and custom fields validation method?
Regarding the “tabs”-plugin:
I think this is way easier to fix, since you could simply switch to the tab the required field is in. What “tabs” plugin do you use @Thiousi?
I’d have to check which one that was. I’ve tested them all. I’ll let you know.
Maybe we should move this to another thread, but I added the “Jump to tab with empty required field on save” functionality to this tabs field.
Only Google Chrome threw an error, since it wanted to focus on the empty field which was hidden and display “Please fill out this field” (See this Stack Overflow answer). That’s why I had to manually add the “novalidate” attribute to the form and disable the Browser validation altogether. It’s not that bad, since Kirby displays helpful warnings itself.
@texnixe Can I split the thread somehow? EDIT: Thank you 
I checked and found that the one I had used and that caused problems with required fields was:
https://github.com/1n3JgKl9pQ6cUMrW/kirby-tabs