(Source: https://www.goatformat.com/home/rulesgame-mechanics)
Since Dueling-Book has a 15-card limit, GoatFormat.com suggests working around this using the following convention:
For "manual" online dueling simulators that restrict you to only 15 cards, use the following convention: Add the 15 Fusions that you think you will be most likely to use, and then if you happen to need one that you didn't add, simply use a different Fusion as a proxy.
Example: You activate Snatch Steal on your opponent's Fusilier Dragon, the Dual-Mode Beast, and use Metamorphosis on it, with the intention of Summoning a King Dragun. But you did not put King Dragun in your 15-card Fusion Deck. You inform your opponent of this fact, special Summon a Darkfire Dragon from your Fusion Deck instead, and say, "This Darkfire Dragon will represent a King Dragun." You then send your opponent a link to King Dragun's text so that they know what it does.
Is this convention recognized on Dueling-Book, in rated Goat Format duels?