I didn't post this in the rulings/bugs forum, because I'm pretty sure I've just forgotten how to you do this.

Basically, certain cards like, Bujin Yamato, have optional trigger effects that activate during the End Phase of a turn.
Effect Veiler negates the effect of a monster, until the End Phase, which is a mandatory lingering effect.

According to the breakdown of the End Phase (as we know it), when both players declare they have not intention of resolving/activating a card, or effect, at that point they MUST activate/resolve any mandatory effects.

Once this has occurred, the game state becomes "open" again, meaning the turn player, and then the opponent can choose to activate further cards, or effects, or proceed to the End of the Turn.

So the problem, I can't remember how to "wait" until Effect Veiler resolves to activate an effect like Bujin Yamato on YGOPro.

Little help?
The game should automatically end Veiler before asking you to activate Yamato at least it did the last time I checked.

Do you have a replay where this occurred?

Yeh, I tried it again, and it only gives the opportunity to activate Yamato's effect while it is still affected by Effect Veiler, then when the opponent passes, the turn ends without any further action.
From that replay, you did not even try to activate it.

Yamato will still have the negate symbol on it but will be able to use its effect. So just click yes.

Next time just upload your replays to the forum directly do not use other sites.