Your wish has already been granted :)
Click on the house icon in the top left then select MAP. When the pop up appears click the Ortho check box and then Grid, move the grid slider to the right to get the grid size you want. then click 2K, 4K or 8K to get a screen shot without the controls.
The screenshot will be stored in the Maps directory wherever you installed Flowscape. For me its: C:\Program Files\FlowScape\maps