Several approaches...
Use the ||< and >|| buttons to place the cursor at the new insertion split point. Then right-click the new clip in the bin (top-right) and Place on Sequence at Cursor.
Or click the first clip to be moved later, hold down <shift> and click the last. Then drag the clips to the right, leaving a gap into which new content can be dropped.
To close any gaps, right-clip them and CLOSE GAP.
Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, that choice is available by clicking the chevron to the right of the Save Project button on the toolbar.