Can you test as below syntax for reference?
(Execute.xml)
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<?xml version="1.0" encoding="ISO-8859-1"?>
<YealinkIPPhoneExecute Beep="yes">
<ExecuteItem URI="Wav.Play:http://10.2.9.5:9/XML_Browser/BackHome.wav"/>
</YealinkIPPhoneExecute>
<!--Below is the test sample template for you.
<ExecuteItem URI="Key:LINE1"/>
<ExecuteItem URI="Key:OK"/>
<ExecuteItem URI="Key:HOTKEY4"/>
<ExecuteItem URI="Dial:12345" />
<ExecuteItem URI="http://10.2.9.5:9/XML_Browser/T46/PhoneDirectory.xml"/>
<ExecuteItem URI="Wav.Play:http://10.2.9.5:9/XML_Browser/BackHome.wav"/>
<ExecuteItem URI="Wav.Stop:http://10.2.9.5:9/XML_Browser/BackHome.wav"/>
<ExecuteItem URI="Command:Reboot"/>
<ExecuteItem URI="Command:Reset"/>
<ExecuteItem URI="Command:ClearCallersList"/>
<ExecuteItem URI="Command:ClearDirectory"/>
<ExecuteItem URI="Command:ClearRedialList"/>
<ExecuteItem URI="Led:SMS=on"/>
<ExecuteItem URI="Led:POWER=on"/>
<ExecuteItem URI="Led:HEADSET=on"/>
<ExecuteItem URI="Led:LINE2_RED=on"/>
<ExecuteItem URI="Led:LINE3_GREEN=slowflash"/>
<ExecuteItem URI="Led:LINE7_ORANGE=fastflash"/>
<ExecuteItem URI="Led:EXP-1-6-RED=fastflash"/>
<ExecuteItem URI="Led:EXP-1-7-RED=on"/>
<ExecuteItem URI="Led:EXP-1-8-RED=on"/>
<ExecuteItem URI="Led:EXP-1-9-RED=on"/>
<ExecuteItem URI="Led:EXP-1-10-ORANGE=on"/>
<ExecuteItem URI="Led:EXP-1-11-RED=on"/>
<ExecuteItem URI="Led:EXP-1-39-RED=on"/>
<ExecuteItem URI="Led:EXP-1-40-GREEN=on"/>
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You can refer to more details in below guide which is the latest one.
Yealink_XML_Browser_Developer_V72