I experimented with the <Disable techs> flag:
Firstly, it needs to be input in this manner:
<DisableTechs>
<DisableTech> <TechType>TECH_POTTERY</TechType>
<bDisableTech>1</bDisableTech>
</DisableTech>
</DisableTechs>
In this example, pottery is shown on the advances screen, but in red. There are arrows pointing to other advances requiring pottery, which are in green - even though they wouldn't be able to be researched either.
Firstly, it needs to be input in this manner:
<DisableTechs>
<DisableTech> <TechType>TECH_POTTERY</TechType>
<bDisableTech>1</bDisableTech>
</DisableTech>
</DisableTechs>
In this example, pottery is shown on the advances screen, but in red. There are arrows pointing to other advances requiring pottery, which are in green - even though they wouldn't be able to be researched either.