It is indeed true that the overall mechanism of handling widgets is bothersome.
KDE
KDE is an international technology team creating user-friendly free and open source software for desktop and portable computing. KDE’s software runs on GNU/Linux, BSD and other operating systems, including Windows.
Plasma 6 Bugs
If you encounter a bug, proceed to https://bugs.kde.org, check whether it has been reported.
If it hasn't, report it yourself.
PLEASE THINK CAREFULLY BEFORE POSTING HERE.
Developers do not look for reports on social media, so they will not see it and all it does is clutter up the feed.
I absolutely agree but I think discuss.kde.org is the best place to, ahem, discuss this issue - more people over there and more chances devs can hear you (and personally I havent' had good experiences with the mods of this community). Maybe even going straight to a bug report because yes, that's a serious UX issue that at least for me has flown over my head if it weren't for you noticing it and talking about it.
Tried to log into the discuss site and it blocked me. Lmfao. The mobile version of it is so bad I entered my password so many times it blocked me.
Just install the widget first, then add it to the panel.
Think of the extra steps as an NPC guiding you back along the proper path for trying to do it in the wrong order.
It doesn't matter how these things are configured, you'll have extra steps if you insist on doing them in the wrong order.
[edit] Why does order matter? Because permissions. Why do permissions matter? Because fundamental OS security.