These are some of the rarer vowel strength in the Sanskrit language.
ḷ is the shortest vowel in Sanskrit language and can be pronounced in different ways. The vowel appears in the verb root of kḷp (kalpate). The English translation of this vowel is “prepare” “happen” “be ready for” “cause” etc.
Let us talk about ḹ. It is even rarer than the previous one. In fact, it is an artificial sound created by traditional Sanskrit grammarians to alternate r sound. It is and alternate version of d and only appears when there is d sound in between.
अग्निमीडे → अग्निमीळे
agnimīḍe → agnimīḻe
I laud Agni -Rigveda 1.1.1