I want to set the "Double click interval". This option exists in the mouse > help center, and according to the information there, it should be under the advanced tab. The actual options do not have advanced tab. However, the help says "Revision Plasma 5.13 (2018-05-18)", so may not be up to date.
Someone had the same problem here: https://forum.kde.org/viewtopic.php?t=153755, however the answers there did not help me, and that post is from Aug 2018.

Here is some information about my version:
Kubuntu 20.04
KDE Plasma Version 5.18.5

This depends on the input driver in use, Kubuntu uses libinput as default where there is no advanced selection for the mouse. There is no other solution than the one in the other forum post.