Hi HJ van Dalfsen,
In the SF 2020.2 it is possible to upload icons and reports but it is not (yet) possible to reuse already uploaded icons and reports. Every object needs it's own (duplicate) icon. If you wish this would be possible, feel free to create a topic in the Ideation section.
Idea is here:
The proposed way by Robert Jan de Nie is a solution to this question but be careful with changing values via SSMS.
Kind regards,
Mark Jongeling
In the meantime, copy the value of the icon column to where you want to use it, using SSMS.
But a more sustainable solution would be to have a per project/version location where an iconset can be uploaded/maintained. On a task or table you should then be able to reference that icon-storage, rather than having icons (duplicated) in multiple places across your project.