Klas and Octopoos team, the SD_Concat plugin page has not been updated with the syntax examples yet. Could it please be added?
Also, in the past, one could include a string in the concatenation, e.g. if I wanted to create an article alias that's a concatenation of "product", separator "-" and the article ID, I'd enter [product]||<content> ... and "-" into the separator box in the field config. However, after the upgrade of Seblod to 3.17.1 the system throws an error on save on the front end: "[product] is a string". The way I got around it is by creating a "dummy" field for the content type with storage 'none' and default value "product". Then in the SD Concat field I enter #product_alias_construct_helper"||<content> and all is well again.