...actually you might not even need the default transponder, just one valid transponder from each satellite should do.
I'm not familiar with either of those satellites but the principle should be the same as for Astra2 (Sky UK);
Make sure your cards are detected
Create a network for your DVB-S card(s) - only specify the network name, orbital position and set 'Network discovery' to 'New muxes + changed muxes'
Click 'Create'
Next add a single multiplex for each of your satellites (I've used Badr/26.2E as the example)
From the 'Muxes' tab click 'Add'
Select the network you just created
In the frequency field, enter 11996000
In the symbol rate field, enter 27500000
In the polarisation field enter H
In the FEC field enter 3/4
In the Modulation field enter QPSK
Leave everything else as is
Click on 'Save'
This should create a single transponder which will contain 'BBC Arabic' and several other channels. Leave TVHeadend long enough and it should automatically start to detect and scan for additional transponders adding the services it finds as it goes.
Same goes for 52.5E Yahsat;
From the 'Muxes' tab click 'Add'
Select the network you just created
In the frequency field, enter 11996000
In the symbol rate field, enter 27500000
In the polarisation field enter V
In the FEC field enter 5/6
In the Modulation field enter QPSK
Leave everything else as is
Click on 'Save'
Again one of the channels on this transponder should be 'BBC Arabic' and again TVHeadend should scan for additional transponders and their associated services.
Give this a go and see how you get on.