DSXchange

I have a sequence which is used in many other sequences. I now want to add a new string parameter to it because a few calling sequences need a "special logic".
The parameter should be empty as a default (so not blank but really an empty string). However, I didn't find a way to do this without changing all jobs. Leaving the default value empty leads to all sequences requesting me to explicitly fill out the parameter on recompilation (without recompilation they actually work correctly but that is not a feasable solution). Is there any way to define an empty string as the default?

Define a parameter at project level with blank value and use that in your sequence so that other sequence would not complain to define that explicitly... I think this should resolves your issue.
If not than please let me know for my learning

I think it would probably work but in accordance with the coding standards here we are not allowed to create project level parameters on our one. These parameters are only allowed to be defined for really global variables...

Then "they" - the makers of the rules - have a problem. Throw it to them.