Is there any chance of getting hyperlinks (a rolling up flap will be a little annoying) to the condition that monsters, spells and magic items cause?

There are plans for such links in the future, this is only the beta and not a finished product yet. Keep checking the forums for updates!

Please add all the other conditions in https://www.dndbeyond.com/compendium/rules/basic-rules/appendices#Conditions and modify the PHB itself.
Some examples of other conditions are (but likely other exist)

• https://www.dndbeyond.com/spells/eyebite (conditions tag is not precise)
• https://www.dndbeyond.com/spells/symbol (conditions tag is simply missing)

BTW when you search for "incapacited" for the spells, you get only these 3 https://www.dndbeyond.com/spells?filter-class=0&filter-search=&filter-condition=7&filter-verbal=&filter-somatic=&filter-material=&filter-concentration=&filter-ritual=&filter-sub-class=
I would suggest when incapacited is selected that all the other conditions including it are also selected.

For spells like Eyebite and Symbol, since multiple conditions are involved, only the first one is displayed in the menu. But if you filter for the condition you desire, the spell is showed:

https://www.dndbeyond.com/spells?filter-class=0&filter-search=symbol&filter-condition=5&filter-condition=14&filter-verbal=&filter-somatic=&filter-material=&filter-concentration=&filter-ritual=&filter-sub-class=