In a terminal, I enter:
PATH=~/.local/bin:/usr/bin lxpanelctl run
In the launcher, I type "tagtime". ~/.local/bin/tagtime exists and is executable by all users.
An error dialog box says: Failed to execute child process “tagtime” (No such file or directory)
lxpanelctl should use the $PATH variable to find the file at ~/.local/bin/tagtime and execute it.
This bug may also be discussed at https://unix.stackexchange.com/q/369878/176171
Because "lxpanel run" just tells "lxpanel" process to launch dialog and then exits immediately, the process showing the dialog is "lxpanel" process, so the PATH the launch dialog is using is the one of "lxpanel" process, not lxpanel process (which already exited).
You can workaround this by putting the dialog
env PATH=/home/yourname/.local/bin tagtime