When using the portable Texstudio 2.8.4 and using the tabulator key, the tabulator is inserted at beginning of the line even if the cursor is between two words (this would be normal only if parts of the line are selected).
Example:
word1 (insert tab here) word2 word3 leads to
<tab> word1 word2 word3 instead of
word1 <tab> word2 word3.
fixed in repository