Gomke

Is there a vector erase tool in Affinity Designer?

I used de library from LibreOffice and it works for Dutch!

I'm sorry, I did not notice it was a 'Mac' topic. I moved to the 'Win' topic.
A solution for implementing the Polish dictionary. Download the files downloaded from https://donate.libreoffice.org/home/dl/src/5.1.3/all/libreoffice-dictionaries-5.1.3.2.tar.xz?idx=2 and place them in the place shown in the screenshot. You can probably use this method for other languages.

Separation preview will be a feature, but I don't think it will happen before the initial release - although I could be wrong?  

A designer specializing in layout work who doesn't know or care about separations is an expensive accident waiting to happen. Black RGB text that prints blurry, or black text at 7pt that's not set to overprint, or images with an RGB black background which auto-separates into rich black that are placed inside a CMYK K-only black rectangle in the hope of it looking seamless – the client is not going to be happy.
I routinely check anything that goes to print in separations preview, and one out of three times, I spot a last-minute problem that needs to be fixed. Partly this is because of idiosyncrasies of InDesign's quirky transparency flattener, but still, it's an important step in any software that helps you prevent costly situations like re-printing 500 000 copies of a document because you missed a very small but very stupid problem.
While in my opinion not absolutely essential for a 1.0 release (a software like Acrobat can be used to check the PDFs if need be), it's definitely far from just a "nice to have" feature.