Re: LaRkana and Sindhi pronunciation
No there is no separate alphabet for ‘Tr’, though the sound exists. It is written as ‘Te/t’. Thats where from the the confusion start. Some people say Te and some Tray for 3 in Sindhi.
An interesting incident I remember. A Sindhi girl (my colleague in office) once told her friends that Sindhi got 52 alphabets. They asked / challenged her to write those 52 alphabets. She wrote around 48 letters and forgot 4 letters in confusion 
She called me for help. I told her 3 missing letters. The last one was ‘jha’ like in the name of Parkash Jha’. When I told her that she said ‘you must be kidding, it can’t be Sindhi alphabet. Ye to urdu main bhi hai’. I said to her ‘aap dobara class one join karen’. 
So there are already some alphabets in Sindhi which are made from the mixture of two letters in other languages, like ‘chh’ in Chhtari is mixture of ‘ch’ and ‘he’ letters of Urdu, but Sindhi got single alphabets for it with four dots 