Hi, the Apple iPadOS app is definitely miss-behaving with Writer’s Find and Replace, good on you for reporting it.
It is easy to reproduce where the dialogue disappears and to bring it back. I didn’t prolong tests until I couldn’t make it appear again. We should log a bug for this, do you want to do this? I can do it if you prefer. Issues · CollaboraOnline/online · GitHub. I was using an iPad Pro running iPadOS 15.4.1, Collabora Office app 21.11.3.5 git hash: eb73aa34.
Find and Replace also misbehaves in Writer in my Chrome OS app, only when the Chromebook is in tablet mode. Not the same problem as you report, but a couple of things I noticed: 1) The top of the Find and Replace dialogue is often missing making it unusable. 2) Highlighted text does not populate the find field when opening the Find and Replace dialogue. Neither of these problems afflict the Apple iPadOS app. I wonder if this should be in the same bug report or a separate one! Not tested on an Android tablet. I was using an Acer R11 running Chrome OS Version 100.0.4896.133 Official Build 64-bit, Collabora Office app 21.11.3.6 git hash: eb73aa34.