Thank you for your answers.
The asset picker is not what I need, because I don't want to pick assets 😉
And I'm talking about the workflow launcher. Sorry that I did not clarify that.
The conditions don't help, because the conditions only check the current status of a value.
What I need is some kind of status has changed launcher.
I believe there is nothing OOTB, that provide something like that, so I think only an exclude-list could do the job (not perfect, but close to it).
Have a look to this:

I have a launcher, that looks on changes on the metadata node. But the launcher should only be triggered, when my own value has changed. The condition only says: has my own value a specific value and NOT has it changed into a specific value. So everytime the asset is changed and the value is like in the condition, the launcher gets triggered, even if my own value has not changed.
My solution: exclude every other attribute, that the metadata-node could contain. In that case, changes on other attributes don't trigger the launcher (I tested it). But I need ALL possible attributes for the metadata node, so I could make a complete exclude list.
Or do you know any OOTB feature to solve this in an easy way?
Best, Maik