Transfer plugin doesn't allow multiple transfers of assets

[mclate]

When using transfer.py plugin it is impossible to transfer assets more than once. Example below is taken from the test file and updated to have one more transfer of already transferred asset:

2010-01-01 open Assets:Bank:Checking
2010-01-01 open Assets:Coinbase  "FIFO"
2010-01-01 open Assets:Binance   "FIFO"

2010-12-25 * "Fill up account with crypto"
  Assets:Coinbase         0.2 BTC {15000 USD}
  Assets:Coinbase         0.3 BTC {16000 USD}
  Assets:Coinbase         0.1 BTC {17000 USD}
  Assets:Coinbase         0.4 BTC {18000 USD, "wow"}
  Assets:Bank:Checking

2010-12-26 * "Transfer lots" #transfer
  Assets:Coinbase        -0.4 BTC {}
  Assets:Binance


; This is expected to result in one more transfer as above
; however, instead it yields "Failed to categorize posting 2"
2010-12-27 * "Transfer some lots back" #transfer
  Assets:Coinbase
  Assets:Binance     -0.1 BTC {}


2010-12-26 * "Transfer the special lot" #transfer
  Assets:Coinbase        -0.4 BTC {"wow"}
  Assets:Binance

[mclate]

Thinking about this further - looks like it isn't possible at all: initial categorization is happening before the plugin, thus it has no clue about such "transfers". In other words, this plugin is only capable of performing a single transition of assets for a single pair of accounts. This is an inherited limitation of the use of "one position with a cost" syntax to do the transfers