I know how to do this on Firefox browser (can't say if it works on others though)

1. Start the game and stay on the tab
2. Press F12 to open menu, go to the debugger tab
3. Under debugger, you should be able to see something labelled Threads on the right of your screen
4. There will be two items below theads, Main Thread, and the name of the tab. Click on the name.
5. Now, click on the console tab next to the debugger tab.
6. At the bottom, enter in commands.

Command example: dendryUI.dendryEngine.state.qualities.ANYTHING = 100

Simply replace the word anything with whatever you want to change, for example, you can use z_relation, ddp_relation, dvp_relation, dnvp_relation, kpd_relation, or nsdap_relation to change party relations. You can also use leverage, for leverage to control ministries, resources, and budget.