In WPS spreadsheets, I keep getting shrunken work area w/ a blank task pane or something on the right. How do I get rid of it to expand the full view?

I have created these spreadsheets with a full screen available. Randomly, some unknown task pane or something appears on the right when I reopen the file. I cannot find how to get rid of or hide that and expand the full usable screen view. It is the blank white area on the far right. [screen print with rogue task pane circled1