In 5.1 the filter widget was prominently shown above the ledger. In 5.2 it is not shown anymore and one has to guess that one has to press Ctrl+F to make is visible. There's no indication in KMyMoney that Ctrl+F will bring it back (except for experts who browse the list of actions in the keyboard shortcut navigation). (see bug 508941) I suggest to add the "Show filter widget" action to the View menu to make it more discoverable. Moreover, I would really like the filter widget to be shown by default again. I have used it regularly and many people will miss this useful feature if it's not shown by default. The location of the filter widget below the list is also quite unusual. All apps that I know and that feature a filter widget show it above the list.
I would call it "transaction search and filter widget" (unless it is under the "Transaction" menu, which I think I prefer, in which case "show search and filter widget") since it does both. If the search/filter widget is shown by default, then it needs a config item to be able to hide it unless explicitly requested. I believe the reason it was hidden was of the space it used - so there is a balance to be found. It is primarily a problem of initial discovery - once a user knows where it is, hitting Ctl-F is easy enough. The problem is not knowing about it at all.
Implemented with https://invent.kde.org/office/kmymoney/-/commit/26bb83b3cc44093a8bbed21af20ebd7b5c577e89