I would like to set the document raster/grid in a 6mm rhythm. I can find the option to set this. But now my grid starts somewhere. I want it to start at the left edge of my page. Is it possible to adjust this? And of course how? Thank you for your help?
To reset your document grid to the top left corner of the page, double click where the vertical and horizontal rulers intersect. If you want to start your document grid from somewhere other than the top left corner of the page, change the zero point of your rulers by dragging from the ruler intersection. This might be useful if you want your document grid increment to sync with your margins.
Note you can also change the origin of the rulers (Preferences>Units and Increments) so that they are aligned to the spine if working on a facing pages spread.