While I understand to a certain degree limiting External Links that lead away from the site, why are links that lead to descriptions such as blinded or grappled etc. not acceptable? I also notice that I have added other people's homebrew creatures etc. that do include "External Links". So why and how?

Is it just how it's typed? Can these links be created in a different way... typing "[condition] Blinded [condition]" or something?  What am I missing?

I have been informed that those links for stuff like blinded and grappled aren’t traditional hyperlinks, they’re “tooltips,” and tooltips do work in homebrews. You can learn all about tooltips here: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/9811-how-to-add-tooltips).

Here's the info via firehawk2324 (Thanks for sharing it with me IamSposta)
I hope this helps others who are/were having the same problem.

D&D Beyond offers the ability to link certain aspects on the forum in mouse-over triggered tooltips, such as magic items, monsters or combat actions - examples being Adult Black Dragon and dash.  To create tooltips in this way as these, use the appropriate [tag][/tag] around the desired subject.

These tooltips can be used in most text boxes on D&D Beyond, such as: forum posts; campaign notes section; homebrew descriptions.

Example: Sun Blade

Use the following within the [ ][/ ] bracket system:

• action - an action taken in combat - e.g. dodge, search and ready
• condition - a condition afflicted upon a creature - e.g. restrained, poisoned and prone
• item - a mundane item - e.g. torch, trident and backpack
• magicItem - a magical item - e.g. Bag of Holding, Dust of Disappearance and Demon Armor.
• monimg - the image for a specific monster (if it has one)
• monster - a creature you can encounter - e.g. Banshee, Bandit and Unicorn
• rule - a rule of D&D - e.g. falling, heavily obscured and three-quarters cover
• sense - a type of extra sense, whether magical or natural - e.g. darkvision, tremorsense and truesight
• skill - this is used for professions - e.g. Persuasion, Stealth
• spell - a magical spell - e.g.  Mage Hand, Magic Missile and Abi-Dalzim’s Horrid Wilting
• wprop - a property of a weapon - e.g. finesse, versatile and heavy
• vehicle - a specific vehicle - e.g. rowboat

Additionally, tooltips support the written text of the tooltip being different from the actual item or monster text. This is great for plurals for example:

Ioun Stones of Strength and Regeneration
would display as:

"Ioun Stones of Strength and Regeneration"

Wolves displays as Wolves

Note: Tooltips do not function in the character sheet. If you create an item with a tooltip to Magic Missile, the tooltip will not be active in the character sheet.