Is it possible to have a saved search show which Custom Form is used for that transaction?

Custom Form is available as a result column.

I thought that results column has been removed. Last time I couldn’t even use {customform} for transactions

Same for me. No custom form in drop down and can't use formula.

That's strange - it's definitely there and working for me (also works as a formula). I'm using a full administrator account, so may be worth considering that if you're using another role? Otherwise may be worth a call to support to see if a particular config option has to be enabled.