Hi, Kristof 

Firstly, I would like to sincerely apologize for the delayed response as we have been experiencing an unusually high number of tickets. I am sorry that it has taken longer than usual to respond to your concern and your patience is highly appreciated.

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1. In main plugin settings >  Render advanced filter , you can set the filters to go into header, like this :

2.

Can i please inspect your table, and check this out?

Not sure if i understood, 

if you wish to manually set the filtering values;  

the only way to change the order of the selectbox/multiselectbox would be to manually add these values in the column settings, under the "Data" tab.

So, access column settings and go to the Data tab. In there, change the type to String (if you haven't already), and change the "Possible values for column" to be "Define values list". Then, below that add the values in the order in which you want them to appear:

And that's the order they will appear in the filter:

Let me know if that helped, please. Thank you