There is no limitation on which content plugins you can use inside FLEXIcontent fields (e.g. in description field, text field, textarea field)

-- Many will work just fine without any alterations.

1. First, plug-ins must be enabled for the particular field, or they will not work, this is parameter "Trigger content plugins"
2. You can trigger plugins selectively per field, parameter "Specific plugins only"

Check the field parameters settings.

Relevant link for third-party extensions working with Flexicontent:

• http://www.flexicontent.org/forum/index.php?f=22&t=494&rb_v=viewtopic
• http://spreadsheets.google.com/ccc?key=0AiGF_obF5dd-dEp5Zkl4Vnp2YTJZX0VIOFI3S0VCZUE&hl=en

http://www.flexicontent.org/forum/index.php?f=27&t=1072&start=0&rb_v=viewtopic

-- Some plug-ins limit themselves to particular components, options, views, etc.
-- Some of these plug-ins may easily be modified to work with other components (e.g. FLEXIcontent).
--Some of these plug-ins may not be easily modified.

--Some have required minor changes to remove their limitations.
--Some will not work without major modifications.

These all depends on the particular plug-in.
-- Many content plug-ins do not work in Sobi2 for the same reasons.
-- Many content plug-ins do not work in VirtueMart for the same reasons