Remember - you need to 'unlock' the parts list before you can make such changes (The small 'lock' button near the top of the window)

If you click 'Delete Row' the row is deleted and everything below shifts up one place.

If you click 'Replace' then the row stays where it is but the 'Add Component' window appears allowing you to select an alternative component and when you insert the new component it appears in the list in place of the old one.

Remember to click 'Save' otherwise your changes will be ignored. (see below)

Note: If you make changes to a common sub-assembly (one that is used in a number of different top level assemblies) then changes to the sub-assembly will affect every top level assembly where the common sub assembly appears.

Whenever you save a Parts List the Save dialog window appears as shown in the picture below.

The Save Dialog always shows the Part Number of the current assembly. (The one highlighted in Yellow on the left).

If you click 'OK' the List will be saved to your database updating the original list. If however you change the name then miniMrp will create a brand new assembly in the database and the original one won't be changed.

In many cases a new assembly is often an updated version of one that already exists so it makes sense to load the old assembly, make the changes as required and save under a new name.