If we analyse a chemical agent and its possible use, we bump into an interesting fact: it is extremely easy to manufacture such agent.
Its handling, weaponizing, and storing make the things complicated!

How to solve this problem?
solution 1
Use a well equipped lab. As it is well known such lab is impossible to be created by an individual...
solution 2
Design your lab according to only one process (for example fluoroacetates or tetramethylenedisulfotetramine). This is a practical solution - anyway it takes months to design such lab.
solution 3
Use binary technique! The final product of your synthesis will be harmess chemicals. When they mix, the toxin will form.
This seems to be a good solution. The only problem is: there are not improvised binary techniques known.

Or they are? Or they will be?

Binaries are not harmless, just less toxic than the intended agent.

The QL precursor that's mixed with sulfur to make VX is more toxic than cyanide, and by contact too, so it's on par with Tabun...NOT harmless.

Plus, that complicates weaponization.

Pick an agent, aqcuire precurors in mass quantities because you know tat after an attack that all such things will become near-impossible to aquire OTC, produce it in mass-quantities, disperse into caches near future targets (to avoid possible discovery by internal security forces during checkpoints after security is increased after your initial attack), then use patsies to deliver your weapons for you so they die during the delivery, leaving the trail cold.

I'm still thinking of crating new binary weapons.
For example metaloorganic + ogranochlorine or some kind of esterification. Organocopper chemicals are interesting (R-Cu-R)Li? I could not find any info on it.

Small molecules like nicotine or atropine could be binrized.
To create simple and safe chem weapons.