I could not find the solution, so maybe this helps to anyone. Possibly even me in the future in case I forget.

In case desklet is no longer relocatable, if you don't want to lose all the configuration there is a dconf trick to make it reappear in the screen area again.

$ gsettings get org.cinnamon enabled-desklets
['simple-system-monitor@ariel:4:1125:875', 'bbcwx@oak-wood.co.uk:5:2350:0']
Second and third number specifies the desklet location on the screen in pixels. To make "bbcwx@oak-wood.co.uk" reappear on the screen enter something like the following:

$ gsettings set org.cinnamon enabled-desklets "['simple-system-monitor@ariel:4:1125:875', 'bbcwx@oak-wood.co.uk:5:1150:0']"