How can I create a line mesh control with points inside the domain (i.e. by prescribing the points coordinates rather than by selecting an existing point)?
You should proceed as follows:
1. Create a 'point spacing'
2. Create a line control. After inserting the line control, you will have in the point entry in the details view two buttons reading 'Apply' and 'Cancel'.
If you select 'Cancel' you then have 'None' in the point selection. You can right-click on 'None' and choose 'Edit'. This then allows you to enter the coordinates of your point (enter 3 numbers separated by a space). Select the created 'point spacing' to set the spacing.
Please take a look at the online help for more details (section CFX-Mesh/Meshing Features/Control).