Launch only one instance of PlanMaker

[ag_me]

If I open a spreadsheet, from File Explorer, an instance of PlanMaker is launched and if I then click on another spreadsheet in File Explorer another instance of PlanMaker is launched.

Where can I configure that PlanMaker will use only one instance to work on multiple spreadsheets ?

[SuperTech]

In PlanMaker, click directly on File | Open to display the Open dialog, clear the New program window option, and open a spreadsheet. This setting is saved and subsequently applies whenever documents are opened. Further spreadsheets opened from File Explorer should then appear as tabs in the existing PlanMaker window.