@ravir73578276,With a sensible guess, this is probably because of the
page that is being edited is using a template (which may be referencing
to basepage.html), which may contain a container wrapper CSS style rule;
this style rule will constrict the maximum width of anything within the
parsys (drag and dropable area). If you want 100% width, you may need to
extend your project's basepage.html, and remove the additional CSS style
rules. Or you can simply directly clean up the basepage.html.