How are Lots used in modern astrology?

I recently researched some Arabian parts and found them interesting. Do they have bearing in a modern chart or are they used for traditional only?

No reason why they couldn't be used regarding the outer planets, but all the information about them I've seen is Traditional. The Modern "equivalent" is midpoint--not the same thing, but similar. Why not give Lots a try, if you have time for it (I do not), and let us know if works for you? You'd have to do some creative thinking for the meanings regarding the Outers. Or if you do find any Modern links, I'd be interested.
Might be a good idea to move your question to the new Modern board to avoid "ruffling any feathers"! And to see if anyone in the Modern category is already using them.

There are several books by modern astrologers which outline new lots often involving the outers; check at Amazon for titles. Both traditional + modernist lots can play a very significant role in chart delineation even if one is applying Purely modernist techniques,

A modern take on the Arabic Parts can be found in Alfred Witte's Rules for Planetary Pictures book. In it he describes a much more extensive list of points (literally several hundred of them) created using various planetary and angle combinations, which he calls "planetary pictures." I believe he includes all of the Arabic Parts in his delineations as well.
Halloran Software's AstroDeluxe software calculates these as "sensitive points" and includes translations of Witte's descriptions as pop-ups (AstroDeluxe also calculates Arabic Parts should you want to cross-reference them).
I think most of us would acknowledge Witte as about as "modernist" as they come...!

When I ran these points on my chart, I got 1,381 sensitive points. Imagine how long it took Witte to calculate those by hand for a client! Then attempt to delineate them! Apparently an orb of 32' is the maximum used with these points. I'm guessing conjunctions only.
I'm not sure if AstroDeluxe calculates all of them, but it calculates a mere 44 Arabic Parts.

Yes, I'm not sure if Arabic Parts are parts of astrology or not. The question here is whether or not any Modernists, ie modern astrologers, used them as part of their modern astrology practices or not. I'm not sure if transits, as you say, are an exclusive part of their use.
Since the Uranian school of astrology (the Germans who invented it did not refer to the astrology they did as that, but as kosmobiologische) invented them, one might assume transits of Uranus might have played a part in their use, or maybe Aquarius.
I think that's partly right.

FraterAC said:

When I ran these points on my chart, I got 1,381 sensitive points. Imagine how long it took Witte to calculate those by hand for a client! Then attempt to delineate them! Apparently an orb of 32' is the maximum used with these points. I'm guessing conjunctions only.
I'm not sure if AstroDeluxe calculates all of them, but it calculates a mere 44 Arabic Parts.

Click to expand...

AstroSeek calculate all parts, even parts that are modern!

FraterAC said:

the Uranian school of astrology (the Germans who invented it did not refer to the astrology they did as that, but as kosmobiologische)

Click to expand...

This is not correct.
Witte's school, originally called the Hamburg school, but which came to be known in English as the Uranian school, is NOT the same as Ebertin's later school which called itself kosmobiologische.
While they did share some characteristics, as the use of midpoints and the 90 degree dial, among others, they are not the same.
My apologies.

FraterAC said:

IThis is not correct.
Witte's school, originally called the Hamburg school, but which came to be known in English as the Uranian school, is NOT the same as Ebertin's later school which called itself kosmobiologische.
While they did share some characteristics, as the use of midpoints and the 90 degree dial, among others, they are not the same.
My apologies.

Click to expand...

The later school that you've said is called cosmobiology in English

The lots are called Arabic Lots if they are used by traditional astrologers, but called astrological lots if they're only used by modern astrologers