Show "Open window" in the task manager item context menu (if the middle click action is set to options other than "open new window")
Thank you for the bug report! However Plasma 6.1.4 is no longer eligible for support or maintenance from KDE; supported versions are 5.27. (LTS), and 6.2 (non-LTS) or newer. Please upgrade to a supported version as soon as your distribution makes it available to you. Plasma is a fast-moving project, and bugs in one version are often fixed in the next one. If you need support for Plasma 6.1.4, please contact your distribution, who bears the responsibility of providing support for older releases that are no longer supported by KDE. If you can reproduce the issue after upgrading to a supported version, feel free to re-open this bug report.
Could you be a bit more explicit about what exactly you want? KDE (and many other) applications that allow multiple windows already have an entry for "Open new window" if the application is already open (and if it's not open yet, you can open it by left-clicking, no matter what middle-click option is selected). But this is there even if middle-clicking opens a new window. I notice that some applications do not have this (e.g. keepassxc). Is this the issue, or is there something specific about the middle-click setting? It's not clear to me how that setting is relevant here.