YEALINK Help - DSS key ID 0
The numbers are used in DSS keys as 'linekey.x.type = 0' 
An active example could be button 1 of the link keys (beside display)

here '27' is used to start an XML browser and return a reply/status...
───────── ───────── ───────── ───────── ───────── 
linekey.1.label = text
linekey.1.line = 0
linekey.1.type = 27
linekey.1.value = http://host/path/file.xml?par=1
───────── ───────── ───────── ───────── ───────── 

or as execute only (no display)
───────── ───────── ───────── ───────── ───────── 
linekey.1.label = text
linekey.1.line = 0
linekey.1.type = 17
linekey.1.value = http://host/path/file.ext?par=1
───────── ───────── ───────── ───────── ───────── 

More downloads / help files at the bottom of this page!
Every type has its own set of parameters.. check the PDFs for details.
EOL  info: yealink MAY provide limited support as these are 'end of life' since 2020-04-01 and stop support at 2026-03-31
!! BE SURE TO GET YOUR FIRMWARE UPDATES BEFORE THAT DATE !!

YEALINK Help - DSS key ID 1
The XXX in 'linekey.XXX.type' could be;
#	Function
---	----------------
0	N/A   (and NO button label)
1	Conference
2	Forward
3	Transfer
4	Hold
5	DND
6 --
7	ReCall
8	SMS
9	Direct Pickup
10	Call Park
11	DTMF
12	Voice Mail
13	Speed Dial
14	Intercom
15	Line
16	BLF
17	URL
18	Group Listening
19 --
20	Private Hold
21 --
22	XML Group
23	Group Pickup
24	Paging
25	Record
26 --
27	XML Browser
28 --
29 --
30 --
31 --
32 --
33 --
34	Hot Desking
35	URL Record
36 --
37 --
38 --
39	BLF List
40	Prefix
41	Zero Touch
42	ACD
43 --
44 --
45	Local Group
46 --
47 --
48 --
49 --
50	Phone Lock
51 --
52 --
53 --
54 --
55 --
56	Retrieve Park
57 --
58 --
59 --
60 --
61	Directory
62 --
63 --
64 --
65 --
66	Paging List
67 --
68 --
69 --
70 --
71 --
72 --
73	Custom Key
74 --
75 --
-----

YEALINK Downloads Page not endorsed by yealink or any other (copy) right holder(s). Some tables are exported for fast reading and to be able to quickly search them. Personal archive.
Yealink ! End of Life Announcement SIP T41P T42G T46G T48G.pdf
Yealink Administrator Guide V86.15.pdf
Yealink Auto Provisioning Guide V83 10.pdf
Yealink AutoProvisioning Template V83.30.zip
Yealink CE T46G.pdf
Yealink Calling and CLIP V81 73.pdf
Yealink Configuration Guide for User Access Level V83 10.pdf
Yealink DECT XML Browser Developers Guide V1.5.pdf
Yealink LDAP Directory V81 73.pdf
Yealink Products Regulatory Notices.pdf
Yealink SNMP Feature IP Phones.pdf
Yealink Server Redundancy V82 21.pdf
Yealink T46G Datasheet V81.pdf
Yealink T46G User Guide V81 90.pdf
Yealink TR 069 Technote.pdf
Yealink Using Enhanced DSS Keys V83 10.pdf
Yealink VLAN Features.pdf
Yealink Wall Mount Installation V1.4.zip
Yealink XML Browser Developers Guide V83 10.pdf
Yealink net 802.1X Authentication V81 73.pdf