Planning new assignments is done in 2 phases:

1) Add modules/assignments to the staging area

Add modules/assignments to the staging area by clicking the plus-icon next to the modules/assignments in the planner.

In this phase, the start date of the module can be changed, one or more modules/assignments can be set up at the same time, and modules/assignments can be removed from the selection by clicking the trashcan-icon.  

2) Plan the modules/assignments

If the selection of modules/assignments is definitive, click the downward arrow to plan the modules/assignments.

At that moment the selected modules/assignments are made available for your client, and he/she will receive an email notification that new assignments are available.

From this phase on it is not possible to remove planned modules/assignments.