Hi
I would ignore intellisense errors until you have a succesful build. Only after a successful build can intellisense paths be updated from the actual results. Intellisense is more lienent because code is treated as work in progress by VS, without a build it has to make some guesses. It's also a good idea to switch off debugging until you have a working project because that adds a lot more to the diagnostics output.
It appears the problem is that your ESP8266_WebServer_Stove.ino code attempts to use Sd2Card, SdVolume, SdFile and I guess they don't exist in the esp8266/2.7.4/libraries/SD library? Does this compile using the Arduino IDE?
You do need to stay within the Arduino Library Specification when working with libraries but you appear to be doing that. The esp compiler will do whatever it is designed to do. You will see in the output that each file is compiled by calling an .exe in the esp toolchain.
[url=https://arduino.github.io/arduino-cli/library-specification/]https://arduino.github.io/arduino-cli/library-specification/[/url]
You can see in the output you posted which libraries are being discovered and from where. For example:
[code]Using library Hash version 1.0 in folder /2.7.4/libraries/Hash"
More info. You wil see these library paths in your output. A few of th 15 libraries you are using
R:/Code/Arduino/libraries/Rtc_by_Makuna
R:/Code/Arduino/libraries/Adafruit_MCP4725
R:/Code/Arduino/libraries/Adafruit_ADS1X15
R:/Code/Arduino/libraries/U8g2
R:/Code/Arduino/libraries/ArduinoJson
braries/SPI
braries/SD
braries/SDFS
braries/ESP8266SdFat
R:/Code/Arduino/libraries/WebSockets
In Visual Micro, you can break the Arduino library location rules and use specific library versions from any location using the checkboxes on the "Add Library" menu however the downside is you loose auto updated when new library versions are released. This auto update or auto discovery is at the heart of Arduino and is recommended. You will see that Arduino allows you to override libraries by putting them in the sketchbook\libraries folder (R:/Code/Arduino/libraries). It is possible that you need a different SD library.