Mouse Broadcasting. MButton, Shift MButton. [PROBLEM]

[Khatovar]

The easiest way to do what you want is to have a triggered key on Window1 send an appropriate key to Window2 instead of trying to send modifiers + mouse. Example :

<Hotkey Shift RButton>
	<If MouseIsOverWindowRect WoW1 0 0 37 37>
				<SendWinM WoW1>
					<Key %Trigger%>
				<SendWinM WoW2>
					<Key Shift 3>

<Hotkey Ctrl RButton>
	<If MouseIsOverWindowRect WoW1 0 0 37 37>
				<SendWinM WoW1>
					<Key %Trigger%>
				<SendWinM WoW2>
					<Key Ctrl 3>

<Hotkey Alt RButton>
	<If MouseIsOverWindowRect WoW1 0 0 37 37>
				<SendWinM WoW1>
					<Key %Trigger%>
				<SendWinM WoW2>
					<Key Alt 3>

Where Ctrl/Shift/Alt 3 are individual healer macros like /cast [@party1] Big Heal /cast [@party1] Small Heal /cast [@party1] Oh S**t Heal. That adds up to a lot of macros, of course, but does not move the mouse at all. This is sort of what I use for proc'd spells.

Alternately, you can use mouseovers where the region determines what is sent :

<Hotkey 2>
	<If MouseIsOverWindowRect WoW1 40 55 54 370>
				<SendLabel w2>
					<Clickmouse Noclick>
					<Key Ctrl 3>
				<SendLabel w1, w3, w4>
					<Key 2>
		<Else If MouseIsOverWindowRect WoW1 95 55 136 370>
				<SendLabel w2>
					<Clickmouse Noclick>
					<Key Shift 3>
				<SendLabel w1, w3, w4>
					<Key 2>
		<Else If MouseIsOverWindowRect WoW1 232 55 30 370>
				<SendLabel w2>
						<Clickmouse Noclick>
					<Key Alt 3>
				<SendLabel w1, w3, w4>
					<Key 2>

Where Ctrl/Alt/Shift 3 are individual healer macros that use mouseover instead of individual targets /cast [@mouseover] Big Heal /cast [@mouseover] Small Heal /cast [@mouseover] Oh S**t Heal. This massively reduces the number of macros needed, as it uses Clickmouse to allow the cursor to move over to the healer window so mouseover can be your targeting parameter instead of needing a direct target. This is what I use for heals.

But, you can still make it work the way you want in your OP using a combination of list, region, trigger and triggermainkey :

<Hotkey CapsLockoff Shift LButton; CapsLockOff Alt LButton; CapsLockOff Ctrl LButton>
	<If MouseIsOverWindowRect WoW1 0 0 37 37>
				<SendWinM WoW1>
					<Key %Trigger%>
						<Clickmouse %TriggerMainKey%>
				<SendWinM WoW2>
					<Key %Trigger%>
						<Clickmouse %TriggerMainKey%>

You may need to putz around with the delays for Clickmouse {Hotkeynet > Options > Settings > ClickMouse > Clickmouse Delays} to get it to get the modifier+Click action reliably.