Hi
Just to clarify I think what Tom means is that Xerte is perhaps not the best tool for summative tests but should be fine for self-assessments and formative tests.
You have to be careful about exactly what page types/interactions you hide/remove the button because some may not work properly if you do this.
After a quick check you could use the following css for some of the page types e.g.:
.x_categories_page #pageContents #button{display:none}
.x_gapFill_page #pageContents #submitBtn{display:none}
.x_textMatch_page #pageContents #button{display:none}
.x_grid_page #pageContents #checkBtn{display:none}
.x_timeline_page #pageContents #button{display:none}
But you need to test this and anticipate all the things a learner might do and ensure things then still work as you wish.
For the multiple choice page add a script optional property to your multiple choice page and then add the following code:
//remove multiple choice button
$("#checkBtn").remove();
again anticipate all the things a learner might do and ensure things then still work as you wish.
HTH
Ron