if I have a sublist of child custom records on a parent custom record, is there any way to control what columns show in the sublist based on the custom form? Let’s say I have parent record A and child record B. Child record B has three fields, “name”, “fish” and “apple”. Parent record A has two custom forms, form 1 and form 2, both which show a sublist of Bs. If I want to show the column for “fish” on form 1 (but not on form 2) and the column for “apple” on form 2 (but not on form 1), is this possible?

You can control sublist columns by custom form on parent record A. Create two sublist views via Customization > Forms > Sublist Views, so one for Form 1 showing "name" and "fish", another for Form 2 showing "name" and "apple". Link each to its respective form under the Sublist tab (Edit Form > Sublist > Select View). Works for child records B’s fields.

This doesn’t work as you describe. I don’t see any way to control the sublist views of child records under Customization -> Forms -> Sublists. In addition, when I edit the form, there is no option to “Select View”. Obviously a user could customise the view themselves but that’s not what we want. We want all users viewing a record of type A to see the same columns for the child record Bs.

Could you make a saved search of your child record and use that as the Sublist instead? Then you could put search a on form A and search B on form B

Unfortunately not, as we need to be able to created and edit the child records from the screen of the parent record.

You can use HTML formulas to replicate the View/Edit link just like the native sublist

for this record type, due to things that need to be triggered in client script on the parent record, all create/edit/delete is done from the sublist on the parent record.